The advertisements on the outside of the cars have always been static two-dimensional pictures, the visual and audio effects thereof being unsatisfactory. Even if the pictures are very vivid, they just flash by when the cars are driving fast past the pedestrians, who are therefore unable to grasp the theme of the advertisements.
In a thriving commercial society, the use of advertising to promote goods or services is extremely important. The propagation of government decrees, campaigns, social activities, and the like is not likely to achieve the desired results if the promotion still stays at the level of using static pictures or signs.